1. Technical Field of the Invention
This invention relates generally to a movable barrier operator that allows travel limit adjustments of the position of a movable barrier after it has reached its normal travel limit, and more particularly, a movable barrier operator that allows for fine-tune adjustment of the travel limits of said movable barrier.
2. Description of the Related Art
Movable barriers have existed in many situations to allow access to a secured area, while at the same time prohibiting access to the same secured area to undesired trespassers. These movable barriers could vary in size, shape, or operation method, but all such movable barriers require an operator that controls the movement of a movable barrier between completely opened and completely closed position. Consequently, such movable barrier operators need a method to determine its travel limits, more specifically the completely opened and completely closed position.
Currently, one approach to movable barrier operator determines the opening and closing positions using cams attached to the shaft of the movable barrier. The cam locations on the shaft determine the completely opened position and the completely closed position of such movable barrier when they come in contact with a limit sensor telling the motor to stop.
Although such a design is simple and works great with broad ranges of movement, it is difficult to obtain fine point adjustment using the above mentioned cams and limit switch combination. Using the cams to set the travel limits may only give rough estimates of the completely open position and the completely closed position because the actual movements of the movable barrier in relation to the cam positions are significantly greater, thus minor adjustment in cam location equates to significant shift in the position of the movable barrier.
Consequently, using traditional adjustment methods often leaves undesirable gaps between the actual position of the movable barrier and the position of the movable barrier in a completely closed or open position. As a result, there is an undesirable gap created between the movable barrier and the physical stopping apparatus.
Traditionally, in order to make such a fine point adjustment eliminating the undesirable gap, a technician has to physically hold down a lever actuator, a limit switch, and the retainer plate, while moving the cam along the notches of the driving shaft. This process requires a complicated procedure that may not easily be achieved by a single technician, thus requiring more than one technician to perform such initial set up. Moreover, in order to make such an adjustment, a technician needs to disassemble the movable barrier operator in order to access the necessary components.
Current products addressing the above mentioned problem of this undesirable gap have used encoders, hall-effect devices, position detectors, learned routines, human intervention, or even trial and error with the already existing cams in the movable barrier operator. However, these methods are expensive, thus making them impractical for gate operator purposes. Moreover, such learned methods require extensive set up time and effort on the part of the installer.
It can be seen that there is a need for a movable barrier operator that is easily adjustable without involving manual adjustment of the cam limits, which may be inefficient and ineffective in small ranges of movement. Moreover, there is also a need that such an adjustment that's capable of fine-tune adjustment capabilities without involving expensive electronic circuitry such as encoders and hall-effect devices. Consequently, there is a need for a movable barrier operator that allows for adjustment of the gap of the movable barrier in the completely closed or open position of the movable barrier without extensive adjustment by a technician.